1. Field of the Invention
This invention is in the field of propellants. More particularly, the invention relates to solid propellant compositions utilizing beryllium hydride as a fuel.
2. Description of the Prior Art
For some time it has been known that beryllium can be utilized as a metal fuel additive in solid propellant formulations. In more recent years, beryllium hydride has been utilized rather than beryllium because it provides the highest theoretical impulse of any known fuel when associated with a wide variety of oxidizers.
One of the more recent and prevalent forms of beryllium hydride utilized in composite solid propellants is BEANE which is produced by the pyrolysis of beryllium alkyls. BEANE has the general formula: ##STR1## WHEREIN: N VARIES FROM 10 TO ABOUT 250 DEPENDING ON THE DEGREE OF PYROLYSIS OF THE BERYLLIUM ALKYL, AND
X and Y can be individually selected from H or R where R is a lower alkyl group of one to four carbon atoms.
BEANE has an intrinsic low density of approximately 0.65 gram/cc. As a result, the material has a large specific volume and surface and thus it is very difficult to obtain high solids loading in solid propellant formulations. One method that has been recently discovered for improving the solid loading capability of the BEANE is to coat the beryllium hydride particles with a fused solid oxidizer composition. The oxidizer coated BEANE particles can then be subsequently incoporated into a composite propellant formulation which could contain from 15 to 25 weight percent BEANE and from 15 to 20 weight percent binder, the remaining being the oxidizer. However, even with the new approach of coating the BEANE with the oxidizer, another major problem remained unsolved.
One of the most prevalent and popular candidates for a binder to be utilized in composite solid propellants incorporating BEANE or beryllium hydride is carboxy-terminated polybutadiene, CTPB. The beryllium hydride, even when coated with an oxidizer, reacts with the acid group of the carboxy-terminated polybutadiene, releasing free hydrogen and precipitating beryllium salts in the polymer. This has severely limited and affected the use of beryllium hydride with carboxy-terminated polybutadiene which otherwise is an excellent binder candidate.